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PhD Final Defense
Pressure-driven tearing and energy transport in finite beta Reversed Field Pinch computations
Date: Friday, May 12th
Time: 10:00 am - 12:00 pm
Speaker: Urvashi Gupta, Department of Physics Graduate Student
Abstract: Pressure-driven effects on magnetic relaxation dynamics and energy transport of an inductively-driven Reversed-Field Pinch device are investigated in a 3D cylindrical magnetohydrodynamics model. Pressure-driven dynamics in RFPs are often assumed to be small. However, unfavorable average curvature in RFPs means that pressure does influence tearing and consequently transport along stochastic field lines. In this work, nonlinear NIMROD computations are applied to model the RFP at experimentally relevant plasma-$\beta$ values. Self-consistent evolution of fluctuations from an Ohmic steady state that includes thermal conduction and heating results in tearing dominant relaxed states with sustained reversal. Linear computations are applied to profiles extracted from the relaxed nonlinear state to study the sources of free energy for the fluctuations. The parallel current drive and pressure-curvature drive for the obtained linear eigenfunctions are found to be comparable and only the sum of both the terms surpasses the stabilizing contribution to drive tearing modes. Energy transport via fluctuation-induced conduction and convection is computed for the nonlinear relaxed states and qualitative agreement with recent experimental results is observed. The heat flux densities are further decomposed to assess the significance of different orders of correlations. The implications of artificial particle diffusion on convective transport and the overall relaxed state are also discussed for this self-consistent MHD model.
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